Abstract
Abstract The dynamic behavior of DNA molecules, when immobilized on DNA microarrays, has puzzled the gene chip researchers. In general, there are two types of immobilization methods, i.e. charge-charge interaction by surface coating and immobilize to the glass surface at one end of DNA molecules. In this study, we will attempt to distinguish weather DNA molecules are like seaweed wavering in a solution or like rope sticking to the surface of glass. The two modes have quite different hybridization efficiency. Qdots can emit the fluorescence continually and stably. The 675 bp, 1699 bp and 2834 bp dsDNA was attached to Qdots in both end. We employ the TIRFM to measure Qdots position and intensity change by time, and estimate the displacement in space. To precise measure the position change of Qdots, we establish the single particle tracking technique, which has the spatial resolution of 18 nm in frame rate 33Hz. To co-operate evanescent wave generated by TIRFM exhibits exponential decay with increasing distance z from the interface of total internal reflection, we detect the relative displacement of Qdots on the Z-axis. The result shows that DNA do like a rope lie on the poly-L-lysine coating surface, but still can get out of the coating surface then shaking. In contrast, on the one end immobilized of DNA molecules like a seaweed just standstill in the water, or swing in the particular two or three position.